Boeing flew the world’s first hydrogen powered plane from an airfield near Madrid, Spain in 2008. The small airplane had extra-long wings and flew for around 20 minutes, proving that the technology worked. Boeing have flown five hydrogen powered aircraft since, but are not the only name looking into this new technology.
Airbus announced that hydrogen-fuelled propulsion systems would be central to a new generation of zero-emission commercial aircraft under the ZeroE project. In September 2020, they presented three concept planes that could be in service by 2035. The first is a turboprop (propeller) aircraft able to carry 100 passengers up to around 1,000 nautical miles (1,850km), the second is a turbofan (jet) plane which would carry 200 passengers around twice as far as the propeller craft. The third concept is a blended-wing design craft that should be capable of carrying even more passengers even further. All of these designs are to be hydrogen hybrid craft, powered by gas-turbine engines that use hydrogen fuel cells and also burn liquid hydrogen as a fuel (see below for more about hydrogen plane types).
In 2016, the world’s first four-seater hydrogen plane took off from Stuttgart Airport, having been developed by the German aeronautical reseach agency (DLR), the University of Ulm, and H2FLY.
In late summer 2020, the California start-up, ZeroAvia oversaw the take-off of a six-seater Piper M-Class plane, called HyFlyer I, that had been fitted to run on hydrogen at a research and development hub at Cranfield airport in the UK.
These early tests and first steps have led to a belief that a commercial passenger aircraft could fly up to 3,000 kilometres by 2035, with a medium-range flight of up to 7,000 kilometres to follow by 2040 or beyond.
Hydrogen was used in flight many decades ago, where it provided buoyancy. However, the Hindenburg disaster of 1937, where the dirigible full of hydrogen gas caught fire, killing 36 people, effectively ended this type of hydrogen use for flight.
Modern hydrogen planes can broadly be split into two types, those that use propellers powered by electricity from hydrogen fuel cells and those that burn hydrogen through an existing yet modified jet engine (as with petroleum). Aesthetically, most hydrogen planes will be similar to traditional ones, except longer to accommodate the larger liquid hydrogen fuel tank.
Not only will these airplanes require on-board hydrogen storage but also the required systems and tubing. In addition, solutions at airports to allow for refuelling with hydrogen will need to be devised and rolled out.
All of this will require standards, codes and regulations to ensure safety, but it is believed that propeller-powered hydrogen planes will have four main components:
- A storage system for liquid hydrogen
- Fuel cells to convert the hydrogen to electricity
- A device to control the power of the fuel cells
- A motor to turn the propeller
As noted above, while much of the current focus is on these smaller, propeller-powered planes, there is also work underway to created hydrogen-powered turbines that would be more efficient at higher speeds.
Hydrogen planes can be either manned or unmanned, such as with hydrogen-powered high altitude platforms (HAPs).
Although hydrogen may offer an emission-free fuel, this doesn’t mean that it is necessarily green. Much of the hydrogen used today is produced by reforming methane from natural gas, which produces carbon dioxide. This type of hydrogen is often referred to as ‘grey hydrogen.’ Carbon capture and storage (CCUS) can be used with this production method to remove the CO2 that is produced, creating what is called ‘blue hydrogen.’
However, ‘green hydrogen’ is certainly the most environmentally friendly type of hydrogen produced. This method uses the electrolysis of water to split water into oxygen and hydrogen. If the electric current that us used for this is produced using renewable energy such as wind power, if becomes a pollutant-free, clean energy source. As the price of renewable energy reduces, so there is more interest in green hydrogen. When this clean hydrogen production is added to the lack of emissions from the planes themselves, we are suddenly much closer to a truly green form of travel.
However, before we reach that goal, there are a series of challenges to overcome…
The challenges around hydrogen powered planes involve factors such as the density and on-board storage of hydrogen fuel, the supporting infrastructure, hydrogen production, and cost:
Jet fuel molecules contain between four and eight times as much energy as hydrogen molecules, meaning that more fuel is needed when using hydrogen. This means that larger fuel tanks are needed, while the hydrogen also needs to be frozen down to minus 253°C in order to liquefy the gas. These factors look set to change the design of planes for longer flights so that, instead of the fuel being stored in the wings as with today’s planes, they will require extra-large fuselages or use blended wings that make the planes look like large triangles. These new designs would not only allow for more fuel storage, but also reduce fuel consumption and improve aerodynamics.
Fleets of hydrogen powered planes will require supporting infrastructure to produce, transport and store hydrogen. This simply doesn’t exist at scale yet and would need to be added to airports around the world. At the moment, the focus is on ground-based vehicles such as luggage-carrying vehicles and airport passenger buses, but as the supporting infrastructure for these vehicles increases, so it will be able to cross over into supporting aviation too.
Most of the hydrogen produced today is created from methane, a fossil fuel that releases carbon dioxide as a waste product. The challenge is to reduce this carbon footprint by producing green hydrogen from water using electrolysis driven by renewable energy. This process is expensive and only about 1% of hydrogen is produced this way, so the challenge is to increase this production while reducing cost.
The cost of hydrogen fuel is currently more than conventional jet fuel, which undermines the push towards green hydrogen flight. Some believe that conventional aviation should be priced to reflect the environmental damage it causes, even if it means higher ticket prices.
With most hydrogen currently being made from fossil fuels, another solution to cut aviation emissions in the near term is the use of sustainable aviation fuels (SAF). These fuels include a range of different products, including biofuels, which result in low net carbon dioxide emissions. Because they are similar to current jet fuels, the can be used with existing systems and infrastructure.
SAFs can be split into two types; biofuels made from the chemical or thermal treatment of biomass like agricultural waste; and electro fuels (‘E fuels’) which are made by reacting hydrogen with carbon dioxide to create ‘syngas.’ This syngas is then converted into ‘e-crude’ by the Fischer-Tropsch process ready for refining into fuel. The SAF production process can be made carbon neutral if the energy required for manufacture is sourced from zero carbon methods.
Can Planes be Powered by Hydrogen?
Although there are still challenges to overcome before we see fleets of hydrogen powered planes, it is possible to power planes with hydrogen.
Is Hydrogen Cheaper than Jet Fuel?
No, hydrogen is currently four times as expensive as conventional jet fuel, although the price is expected to drop over the coming years as infrastructure improves.
Can Turbine Engines Run on Hydrogen?
Gas turbines can be configured to use green hydrogen either by installing new units or upgrading existing ones.
With zero CO2 emissions, hydrogen powered planes could prove to be a good solution for environmentally friendly flying. It is estimated that hydrogen combustion could reduce the climate impact of flight by 50-75%, and with fuel-cell technology by 75-90%.
However, in order to reach the goal of clean hydrogen planes flying around the world there needs to be an upscaling in green hydrogen production and a reduction in price.
The first steps are being taken to create this infrastructure with Group ADP already teaming up with Air France KLM and the Paris Region to turn Parisian airports into ‘hydrogen hubs,’ beginning with the support for hydrogen trucks, logistics, ground handling, and more.
Such initiatives need to be rolled out elsewhere in order for hydrogen to truly become part of meeting climate neutrality goals set out in the European Green Deal and elsewhere. The European Green Deal has set out plans to decarbonise hydrogen production through the use of renewable energy rather than fossil fuels, with the aim to see renewable hydrogen technologies deployed at scale from 2030 onwards.